1. Technical Field
This invention relates to a projector and a method for manufacturing a projector.
2. Related Art
Traditionally, a projector having a first lens array, a second lens array and a superimposing lens as a light equalizing system has been known, for example, as disclosed in JP-A-8-304739 (FIG. 11). In the traditional projector, since light having relatively uneven in-plane light intensity distribution emitted from a light source is converted to light having relatively even in-plane light intensity distribution by the function of the first lens array, the second lens array and the superimposing lens as the light equalizing system, such light having relatively even in-plane light intensity distribution can be cast to an image forming area in a liquid crystal device as an electro-optic modulator, which is an illumination target.
However, the traditional projector has the following two problems.
First Problem
In the projector, if an image forming area in the electro-optic modulator cannot be accurately illuminated, the brightness of a projected image projected on a projection surface is lowered or the edge of the projected image is shaded. Thus, in consideration of the dimensional error, mounting accuracy and the like or optical elements themselves in an illumination system and a color separation light guiding system, a predetermined illumination margin is provided around an illumination area of illuminating light cast to the image forming area. The design is made so that the image forming area in the electro-optic modulator securely falls within the range of the illumination area including the illumination margin.
Meanwhile, it is preferable that the size of such an illumination margin is as small as possible. This is because, if the size of the illumination area including the illumination margin is increased unnecessarily with respect to the image forming area, the illuminance in the image forming area is lowered accordingly and the brightness of the projected image protected on the projection surface is lowered. To minimize the size of the illumination margin and match the illumination area with the image forming area, the size of the illumination area must be adjusted.
Traditionally, when adjusting the size of the illumination area, for example, the position of each optical element (for example, first lens array, second lens array, superimposing lens and the like) in the illumination system is adjusted and the size of the illumination area is thus adjusted. However, such work requires much time and labor. Therefore, the traditional projector has a problem that it is not easy to adjust the size of the illumination area.
Second Problem
Recently, in order to reduce the cost of the projector, miniaturization of the electro-optic modulator is highly demanded. If the electro-optic modulator is miniaturized, the size of the image forming area is reduced, too. Therefore, the size of the illumination area must be reduced in accordance with the size of the image forming area.
Here, the size of the illumination area is calculated by multiplying the size of first small lenses of the first lens array by the ratio of the focal length f2 of the superimposing lens to the focal length f1 of second small lenses of the second lens array (=f2/f1 (magnification)). Therefore, in order to reduce the size of the illumination area, the size of the first small lenses must be reduced or the focal length f2 of the superimposing lens must be reduced, or the focal length of the second small lenses must be increased.
However, in order to reduce the size of the first small lenses, the first lens array must be changed to a first lens array in which each small lens has a reduced size. In order to reduce the focal length f2 of the superimposing lens, the size of the color separation light guiding system must be reduced in order to increase the focal length f1 of the second small lenses, the size of the illumination system must be increased. That is, in order to reduce the size of the illumination area, the illumination system (including the first lens array) or the color separation light guiding system must be changed.
Therefore, the traditional projector has a problem that, if the electro-optic modulator is miniaturized, the illumination system or the color separation light guiding system before the change of the electro-optic modulator cannot be used as it is.
This problem occurs not only when the electro-optic modulator is miniaturized but also when the electro-optic modulator is increased in size.
That is, the traditional projector has a problem that, if the size of the electro-optic modulator is changed, the illumination system or the color separation light guiding system before the change of the electro-optic modulator cannot be used as it is. As a result, the illumination system or the color separation light guiding system must be redesigned. Therefore, the number of processes increases because of the redesign and the manufacturing cost of the projector increases.